1. Field of the Invention
The present invention relates to a technique in a case in which tissue strain imaging (TSI) is applied to elastic imaging to estimate a local hardness distribution from the strain state of a biological soft tissue.
2. Description of the Related Art
In ultrasonic diagnosis, the pulsation of the heart or the movement of a fetus can be displayed in real time by the simple operation of bringing an ultrasonic probe into contact with the surface of the body. In addition, this technique is highly safety, and hence allows repetitive examination. Furthermore, the size of this system is smaller than those of other diagnosis apparatuses such as X-ray, CT, and MRI apparatuses, and hence can be said to be a simple diagnosis technique which facilitates examination to be performed by moving the apparatus to the bed side. Ultrasonic diagnosis apparatuses used in this ultrasonic diagnosis vary in type depending on the functions which they have. Some compact apparatuses which have already been developed are small enough to be carried with one hand. Ultrasonic diagnosis is free from the influence of radiation exposure such as X-ray exposure, and hence can be used in obstetric treatment, treatment at home, and the like.
It is very important for tissue diagnosis to objectively and quantitatively evaluate the function of a living tissue such as cardiac muscle by using such an ultrasonic diagnosis apparatus. For example, there has recently been commercialized, as a quantitative evaluation method for the heart, a technique of calculating local myocardial wall motion information such as displacement or strain while performing local pattern matching in images (see, for example, Jpn. Pat. Appln. KOKAI Publication No. 2003-175041). There is available a technique of accurately computing the three-dimensional distribution of myocardial wall motion information by using an ultrasonic diagnosis apparatus capable of acquiring three-dimensional images (see Jpn. Pat. Appln. KOKAI Publication No. 2003-175041). These techniques allow to acquire three-dimensional myocardial wall motion information and the like and quantitatively evaluate the function of a tissue.
As an image diagnosis technique using an ultrasonic diagnosis apparatus, a technique called elastic imaging is available. This technique applies a dynamic load to a tissue to compress/expand it, and measures a motion (dynamic response) in response to the application of the load, thereby acquiring and visualizing elastic information. Recently, there has been developed a technique of determining and displaying the current pressed state (pressing strength) by using displacement information obtained from between two frames when performing this elastic imaging (i.e., a technique which applies TSI to elastic imaging) (see, for example, Jpn. Pat. Appln. KOKAI Publication No. 2004-351062).